The cougar — stealthy, silent and cunning in the wild — has proven equally elusive in evading attempts to monitor the big cats' visits to the tourist mecca of Yosemite Valley.

Les Chow, a cougar expert and wildlife biologist with the U.S. Geological Survey, spent four years, from 1998 to 2002, pursuing that goal.

With a pack of hound dogs, and in the company of expert trackers, Chow would set off early in the morning when he and his team spotted mountain lion tracks on rim trails in the high country of Yosemite National Park, which traced the upper rim of the seven-mile-long Yosemite Valley.

"We almost always found lion tracks," he said. "They're using the trails, and they're using them frequently."

Cougars also are called mountain lions and pumas, among other names.

"They have soft feet," he said. "They don't like walking on rocky stuff."

With his pack of six or so keen-nosed dogs, an expensive breed called Walker treeing hounds, the trackers would pursue any faint cougar scent.

If they were able to tree a cougar after a chase, Chow would shoot it with a tranquilizer dart and then wrap a radio collar around the temporarily immobilized animal's neck to track its movements once it disappeared back into the wild.

During the four-year period he pursued them, Chow collared seven cougars inside or near the park boundaries, but none in Yosemite Valley itself.

In addition, none of the collared

animals ever entered into the enclave of Yosemite Valley, where the majority of tourists visit.

The historic flooding of the Merced River across Yosemite Valley on Jan. 1, 1997, provided Chow with a unique opportunity to chase cougars in the popular destination, noted worldwide for its soaring 3,000- to 4,000-foot granite walls and stunning waterfalls.

The devastating flood, which damaged pipelines, roadways and buildings, closed the park to visitors from Jan. 1 to mid-March of that year.

After the river receded, but with the valley still empty of tourists, Chow said he could let the dogs run loose without fear of creating pandemonium at the spectacle of a pack of baying hounds tearing across roadways and meadows.

"It would be a circus. And once you start a chase, there's really no way to stop it," he said.

"The dogs are too valuable to get hit by a car," he added. A skilled tracking hound can cost as much as $10,000, Chow said.

But he said he could not get approval from the National Park Service to run the dogs on the valley floor. When his four-year quest to quantify the comings and goings of cougars in Yosemite Valley ended unsuccessfully, he did not ask for a renewal of the project.

"I couldn't accomplish what I set out to do," Chow said. He said he still has no estimate of how many cougars regularly enter the valley.

However, he estimates that 25 to 50 cougars use the backcountry of Yosemite National Park, with numbers declining in the winter.

But he and his team did get a sense of the frequency of cougar forays by monitoring tracks on pathways into Yosemite Valley from the high country above, such as in gulleys or next to creeks.

"We rarely found indications they were coming into the valley," Chow said, though he noted cougar sightings are reported annually in the valley.

For those that did come, "they'd be there four to six weeks," he said. "And then they'd be gone."_________________13years of dedication Studying "Cougars" taking sighting reports, Tracking & Filming the wild!